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Presented By: Funky Monkeys, Team 846 Available online at Resources > WRRF Presentations.

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Presentation on theme: "Presented By: Funky Monkeys, Team 846 Available online at Resources > WRRF Presentations."— Presentation transcript:

1 Presented By: Funky Monkeys, Team 846 Available online at Resources > WRRF Presentations

2 Presented by: Miles Chan

3 Drivetrain Requirements  Common Features: Fast Easy to turn High acceleration  FIRST Competition Demands: Point-to-point movement Turn in place Push hard

4 Ackerman Steering Team 34’s Design on Chief Delphi

5 Differential/Tank Steering  Power left and right sides independently  Features Simple Easy to drive Pushes hard

6 4 Wheels Differential Steering Wheels slide to turn

7 Ability to Turn  Wheels generate force while friction resists Turning Torque – Resisting Torque

8 Terminology:  µ = Coefficient of Friction  Weight = Weight of the robot  F = Force  T = Torque Track (W ) Wheelbase (L)

9 Maximum Tractive Force Per Wheel ( F TMax ) Track (W ) Wheelbase (L)

10 Maximum Turning Torque (T TMax ) Track (W ) Wheelbase (L) W/2

11 Maximum Resisting Torque (T Resisting ) Track (W ) Wheelbase (L) L/2

12 Turning Torque v. Resisting Torque

13 4 Wheel Layout  Remember: Turning Force – Resisting Force Only wide robots can turn

14 6 Wheel Layout  Weight spread over 6 wheels  Only 4 wheels resist turning

15 Turning Torque v. Resisting Torque

16 6 Wheels Dropped Center  Center wheels dropped about 1/8 inch Improvement of 33% - 100% Rocks on center when turning 30% 10%

17 2 Wheels, 2 Omniwheels  Omniwheels 90° rollers allow sideways motion  Center of rotation between non-omni wheels  4 wheels provide tractive force  No Wheels Resist c c c c c c

18  Wheel modules rotate  Advantages Translational movement Pushes hard  Disadvantages Complicated design Increased need for driver training Requires additional steering motor Swerve Drive Craig Hickman’s Design on Chief Delphi

19 Mecanum Wheels 45° Rollers allow lateral movement

20 Mecanum Drive  Demo: eature=related eature=related  Advantage Translational movement  Disadvantage More gearboxes Expensive wheels Low pushing force

21 How it works: Forward movement

22 How it works: Sideways movement

23 Videos  Omni, Mecanum, Swerve drive examples  Nona-drive (variant of Slide Drive) feature=related feature=related

24 Conclusion  Exotic Drives Cool factor May give key advantage in a particular game.  Tank Drivetrain Simple solution - rugged & reliable

25 Presented by: The Funky Monkeys Team 846 Akshat Agrawal, Anurag Makineni, and Jackie Zhang

26 Power Distribution Diagram Robot Controller

27 Battery  12V Lead Acid Battery (18Ah)  13 Pounds  Provides over 100 amperes of current. Total output of over 1200 watts of power.  Can supply over 700 amperes of current when terminals are shorted.

28 Robot Power Switch  Used to turn robot on and off, including emergency shut off  Also a 120 amp circuit breaker  Must be placed in an accessible location

29 20-40 Ampere Fuse Location Branch circuit power connection Main Power Circuit connection Power Distribution Board

30 DC To DC Converters  Used to change voltage coming from battery to specific voltage required in branch circuit 12V-5V 12V-24V (for robot controller)

31 Power Distribution Diagram Robot Controller 40A 20A 100A 18AWG 12AWG 6AWG

32 American Wire Gauge  Sizes are based on the AWG (American Wire Gauge) System AWG sizes are based on number of wire draws – Higher gauge = thinner wire

33 Motors (FRC 2011) Name# in KOPAdditional AllowedTotal CIM224 BaneBots404 Fisher Price101 Window Motors404 Automotive Window Motor Worm Gear RS Series Motor CCL Industrial Motors Limited (CIM)

34 Robot Controller CompactRio National Instruments Embedded Controller  The “Brain” of the robot Sends control signals to components  In 2012, rookie teams will receive new smaller cRIO. Costs $525 for veteran teams Costs $285 without I/O modules

35 cRIO Specs  2012 cRIO-4 Slots Power o 24V Power via PD Board Proccessor o 400 MHz o Freescale MPC5125 Memory o 256MB System Memory o 512MB Storage Memory Software o VXWorks Operating System o Lab View, C++, Java o Has an Field Programmable Gate Array (FPGA) allows for real time access to the robot

36 PROBLEM!  The cRIO cannot directly control the motors. Cannot provide enough power – will get fried if that much power runs through it.  Solution Intermediary Motor Controllers o Relays o Electronic Speed Controllers

37 Spike Relays  Relays close or open the circuit based on signals from the cRIO.  Use an H-Bridge

38 How an H-Bridge Works MOTOR +12V Ground S1 S3 S4 S2 S1+S4 FULL FORWARD S3+S2 FULL REVERSE S1+S3 BRAKE

39 Electronic Speed Controller (ESC)  Control the amount of power sent to the motors in addition to direction that motor turns.  Two types of ESC’s: Victor 884 ESC Jaguar ESC

40 Speed Controller Comparison Jaguar ESC Larger Communication via: Servo Wire CAN-bus Victor ESC Smaller Communication via: Servo Wire

41 Pulse Width Modulation (PWM)  Pulse Width Modulation is used in two ways on our FIRST Robots: 1. To provide a varying amount of power to the motors. 2. To communicate with the Speed controller.

42 Variable Power Delivery  The Speed Controller varies the power delivered to the motors by changing the “Duty Cycle.” 12V 0V PERIOD ( ms ) DUTY CYCLE (%) = TIME ON PERIOD 12V 0V DUTY CYCLE

43 Speed Controller Communications  There are two ways to communicate with the ESC 1. CAN-bus o Uses “Message based protocol” (like Ethernet) 2. Servo Cable o Uses Pulse Width Modulation

44 Speed Controller Communications using PWM  RC Model Aircraft standard:  The width of the pulse is measured as unit of time. Time which each pulse lasts is the pulse width.  Signal: 1.5 ms ± 0.5 ms 40 ms (20ms-50ms)  2.0 ms = full forward  1.75 ms = 50% fwd  1.5 ms = off  1.0 ms = full reverse

45 CAN-Bus  “CAN” Stands for “ Controller Area Network”  Is a single chain of point-to-point connections  The “bus” goes around the chain delivering the signal to different addresses – each ESC has its own address 2 CAN ESC cRIO ESC

46 How does the CAN-bus simplify wiring? ESC cRIO ESC 2 CAN ESC cRIO ESC (Daisy Chaining) Although the amount of wires is the same in each case, without the CAN-bus, the wires have to stretch all the way across the robot from the cRIO to each ESC, whereas with the CAN-bus, they are all linked together in a single chain.

47 CAN-Bus Wiring  Telephone-style RJ11 instead of servo wire  Easy to make custom length with crimp tool  Can’t be put in backwards Servo Wire Telephone Wire

48 Power Distribution Diagram Robot Controller

49 Presented by: Brian Axelrod

50 Presented by: Brian Axelrod

51 Why use sensors?


53  Increased performance Speed Preset Positions  Safety Prevent robot from damaging itself

54 Limit switch  A simple switch  Can be set up to be triggered near a physical limit  $

55 Hall effect sensor  Detects a magnetic field  Longer range  Can switch much faster than a mechanical switch  $

56 Potentiometers (Pots)  Sensor for measuring position: Rotation, distance, etc.  $

57 Potentiometers (Pots) +5V Ground/0V 5V 2.5V 0V +5V GND Output Simplest type: Slider Slider is connected to output. 10 K Ω +5V Ground/0V 100% 50% 0%

58 Types of Potentiometers (pots)  Slide  Rotary

59 Pots: Uses  Sense position: e.g. lift  How to sense the lift position? Travel length is 6 feet No linear pot long enough

60 Multi-turn Pots  Multi-turn pot: Usually 3, 5, or 10 turns $$  Alignment is important! Continuous rotation: use encoder

61 Reading the Value  Analog voltage level  Analog-to-Digital Converter (ADC) Converts to number 0-1023 for 10-bit ADC Comes in kop with cRio as analog module 8 ports  Easy to implement in code m_liftPot.GetAverageValue()

62 Optical Encoders Optical Sensor (A) to controller Optical Sensor (B) to controller A ChannelB Channel

63 Optical Encoders Optical Sensor to controller Optical Sensor to controller

64 Optical Encoders  Determining Distance Travelled Count pulses  Determining Speed Distance over time Time over distance

65 Other Encoders Our 2006 robot’s ball launcher Hall Effect Sensor, and embedded magnet in wheel using encoder as a speed sensor

66 Yaw Rate Sensor/Gyro  Also commonly known as a gyro  Indicates rotational velocity

67 Accelerometer  Measures acceleration  Detects gravity  Going above max acceleration will give you wrong readings  Detect if going up a bump straight

68 Sensing Distance: Ultrasonic Sensors  Determine distance  Send pulse of sound  Measure time until echo

69 Infrared Proximity Sensors  Determines distance to object in front of it  Analog voltage reading  vs. ultrasound: Shorter range More accurate

70 Camera  Not a magic bullet  Can choke your machine  Image processing  Can sense enviroment

71 Kinect  Still not a magic bullet  RGB-D  With proper processing easier to make reliable Depth image not dependant on lighting

72 Conclusion  Never rely on the operator to do the right thing  Useful for adding functionality and as safety features  Large variety of sensors that can detect a variety of parameters  Can buy sensors at Trossen robotics Digi-key Mouser Acroname

73 Michael Lin and Eric Yeh presents…

74 Pneumatics - Definition  Pneumatics is the use of pressurized air to achieve mechanical movement Jack Hammer Nail gun Drill Pneumatics?

75 Overview of Pneumatics

76 From FIRST pneumatics manual

77 Compressor  Source of energy in pneumatic system Can Generate up to 120 PSI  Compacts air

78 Diaphragm pump

79 From FIRST pneumatics manual

80 Common Valves and Fittings  Pressure switch, Release valve, Plug valve,

81 From FIRST pneumatics manual

82 Regulator  Maintains a constant level of pressure. Working air pressure  Maximum of 60 psi for FIRST competitions

83 From FIRST pneumatics manual

84 Actuators  Actuators convert the difference in air pressure to mechanical motion Takes the working air and makes it into mechanical motion  Linear actuators (also known as cylinders)  Narrower actuators move more quickly

85 From FIRST pneumatics manual

86 Solenoid Valves  Controlled by the robot’s CPU  Solenoids opens a port to pressure when a voltage is applied  Double solenoids controls two ports When one port is open, the other is closed Festo single solenoid valveFesto double solenoid valve

87 From FIRST pneumatics manual

88 Tank  Tanks are a reserve of compressed air  Maximum of 120 psi for First competitions

89 89 Finding Linear Force 89

90 90 Finding Linear Force 90

91 91 Finding Linear Force 91

92 Forces of Different Bore Cylinders at 40 psi and 60 psi Bore (inches)0.751.502.00 Extending (40 psi)18 lbf71 lbf126 lbf Retracting (40 psi)16 lbf65 lbf113 lbf Extending (60 psi)26 lbf106 lbf188 lbf Retracting (60 psi)24 lbf97 lbf170 lbf From FIRST pneumatics manual


94 94 Finding Linear Force 94

95 Conclusion  Covered major components of FIRST robots  Slides available at Resources > “WRRF Presentations”

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